The invention relates to an apparatus for storing data of a device which is to be monitored, in particular of a motor vehicle, in which apparatus the data are advantageously stored in a memory unit by means of a control unit.
DE 196 25 619 C2 discloses a method for storing data in a motor vehicle, in which adaptation data which are used to control the motor vehicle are firstly read into a first memory and, when the velocity of the motor vehicle drops below a predefined value, said data are read out of the memory again and stored in a second nonvolatile memory.
Such adaptation data are, in this context, control data which the control program requires to ensure the operation of the vehicle. During the service life of a control unit, the operational parameters of the device which is to be controlled by the control unit, in particular the motor vehicle, change. The control data therefore have to be continuously newly determined and the newly determined data have to be stored. In this way, it is possible to adapt the control programs to changes in the operational parameters of the device which is to be controlled.
Owing to the development of electronics in motor vehicles, an increasing amount of operational data has to be generated and adapted during the service life of the vehicle. Usually, a nonvolatile read-write memory is specially provided for storing the operation-dependent data. In order to execute a control process of the motor vehicle, the corresponding data are called from this read-write memory and processed by the central arithmetic unit. The NV-RAM""s which are usually used as read-write memories are driven serially, which gives rise to long processing times.
The invention is thus based on the object of providing a device which makes it possible to store in an operationally reliable way and with a high processing speed a large amount of data which change continuously during the service life of the motor vehicle.
The object is achieved according to the invention in that the fixed data and the continuously updated data of the device which is to be monitored are stored in the memory unit which contains the open-loop and/or closed-loop processes.
The advantage of the invention consists in the fact that by using a memory containing open-loop and closed-loop programs to permanently store operation-dependent control data of the motor vehicle it is possible to dispense with one or more read-write memories. The fixed program code and the nonvolatile data are stored in a single electronic component, which results in a reduction in hardware. This reduction in hardware is a decisive advantage, in particular in view of the ever more complex electronic open-loop and closed-loop control systems which are being applied in motor vehicles, and because the installation space available in motor vehicles is becoming smaller and smaller, these things being an advantage because they permit a decisive reduction in costs.
In one refinement, the data which are to be updated are stored in an area of the memory unit which is permanently defined by the addresses of individual memory locations. This permanently addressed area makes available an easy-to-manage grouping of memory locations, which is utilised exclusively for cyclically storing driving-specific operational data and control data.
As an alternative to this, these data may be stored in an address space which is dependent on the physical organisation of the memory unit.
A different reading and clearing cycle can be implemented particularly easily when the defined area of the memory unit is divided into at least two sectors. When at least two sectors are used, it is ensured that each clearing procedure can be preceded by a writing procedure performed on the updated data.
Here, firstly the first sector of the defined area of the memory unit is completely filled with the operational data, and the first sector is not completely cleared until after data have been written to the first memory locations of the second sector. This ensures that the first sector of the defined area is not cleared until it has been ensured that the data stored in the second sector of the defined area are free of errors. In the event of errors, it is still possible to fall back on the data from the first sector in order to execute the open-loop and closed-loop processes.
The cycle rate of the possible storage operations increases in particular if data are alternately written to the two sectors of the defined area of the memory unit. This results in multiple use of the memory locations arranged in these sectors.
Writing data alternately to a plurality of sectors correspondingly increases the maximum permissible number of writing and clearing cycles of the memory unit.
The memory unit is advantageously an electrically clearable memory circuit. Commercially available flash modules can be used for this purpose.
In one refinement, the control unit is a device in the motor vehicle for controlling the distance between vehicles, which device stores, in a predefined time slot pattern, both object data and data relating to vehicle dynamics as operation-dependent data. Using the storage possibility according to the invention with such a device for controlling the distance between vehicles increases considerably the cycle time despite a large amount of data which are to be stored, comprising, for example, the distance and relative speed of the vehicles travelling in front, the coordinates of the driving corridor, and the velocity and acceleration of the motor vehicle which is to be controlled.